Package org.geotools.vectortiles.store

Class VectorTilesRequestScale

Object
VectorTilesRequestScale
public final class VectorTilesRequestScale extends Object
Hook to provide a requested scale denominator for VectorTilesFeatureSource.determineZoomLevel(org.geotools.api.data.Query), superseding the GEOMETRY_GENERALIZATION and GEOMETRY_DISTANCE hints provided by the renderer.

Rationale being that StreamingRenderer computes the generalization distance in a way that's inconsistent with the map scale, results in different values for different tiles on the same map, and often, especially when doing reprojection, the generalization distances result in querying much higher tile levels than it should, leading to traversing too many tiles from the PMTiles or other vector tiles datastore. It also always performs the query in the layer's native CRS.

Usage: 


 try {
     VectorTilesRequestScale.set(scaleDenominator);
     // perform feature source queries...
 } finally {
     VectorTilesRequestScale.clear();
 }

When set, the scale denominator is converted to a resolution using the OGC standard pixel size of 0.28mm (0.00028 meters): resolution = scaleDenominator * 0.00028

See Also:

  • Method Details

    • set

      public static void set(double requestScale)
      Sets the scale denominator for the current thread's vector tile requests.

      The scale denominator represents the ratio between a distance on the map and the corresponding distance on the ground. For example, a scale denominator of 50000 means 1 unit on the map equals 50000 units on the ground.

      Parameters:
      requestScale - the scale denominator value (e.g., 50000 for 1:50,000 scale)

    • get

      public static OptionalDouble get()
      Returns the scale denominator set for the current thread, if any.
      Returns:
      an OptionalDouble containing the scale denominator if set, or an empty optional if not set

    • clear

      public static void clear()
      Clears the scale denominator for the current thread.

      This method should be called in a finally block to ensure proper cleanup and prevent memory leaks in thread pool environments.